1. Technical Field
The invention relates to a method for manufacturing a MEMS device for use in, for example, the ejection of a liquid from a liquid ejecting head provided in an ink jet type recording head or the like, a MEMS device, a liquid ejecting head, and a liquid ejecting apparatus. The invention particularly relates to a method for manufacturing a MEMS device formed by a plurality of substrates joined by an adhesive, a MEMS device, a liquid ejecting head, and a liquid ejecting apparatus.
2. Related Art
As micro electro mechanical systems (MEMS) devices used in liquid ejecting heads, there are devices formed by joining a plurality of substrates in a stacked state using an adhesive. Such a MEMS device is provided with a liquid flow path in communication with a nozzle, a movable region for ejecting the liquid in the liquid flow path from the nozzle by generating pressure fluctuations, and the like. For example, with the ink jet type recording head described in JP-A-11-227190, a MEMS device is described in which a substrate where a pressure chamber is formed, a vibrating plate that blocks an open face on one side of the pressure chamber, and a piezoelectric element that displaces a movable region in the vibrating plate corresponding to the pressure chamber are stacked. In this configuration, a silicon single-crystal substrate is used as the substrate forming the pressure chamber (hereinafter referred to simply as the “silicon substrate”), and the pressure chamber is formed by etching the silicon substrate. When removing a mask that is used for forming the pressure chamber by wet etching, the vibrating plate (insulating film) exposed in the pressure chamber is also exposed to the etching solution and, consequently, the vibrating plate is also etched (isotropically etched) to a point partway through the plate in the thickness direction. Moreover, when side etching (undercutting) progresses to the bottom of the wall defining the pressure chamber, an eave portion is formed in the opening edge of the vibrating plate side of the pressure chamber.
With the configuration described in JP-A-11-227190, the side etching proceeds past the opening edge of the pressure chamber and is performed on the vibrating plate and consequently, compared to a configuration in which the vibrating plate is not etched, the area of a movable region of the vibrating plate, which is displaced by the driving of the piezoelectric element, is expanded to the extent equal to the side etching. Plate thickness of the movable region is less than plate thickness in other portions of the vibrating plate. Consequently, damage such as cracks and the like readily occur in the vibrating plate due to the displacement of the movable region. Additionally, the area and the thickness of the portion that, in effect, functions as the movable region are dependent on etching accuracy and, therefore, there has been a risk of variation occurring in the vibration characteristics of the movable region (e.g. the amount of displacement and natural vibration frequency when a given external force is applied).